The art is replete with disclosures of nonphosphated granular cleaning compositions, often containing esoteric ingredients. Numerous processes have been disclosed for their making. However, the practical formulator is often confronted with problems stemming from a need to incorporate commercially available ingredients into the composition's matrix using conveniently accessible processing equipment. Unfortunately, equipment available to the formulator is likely to have been designed to give excellent results in the days when most of the ingredients of automatic dishwashing compositions were inorganic (e.g., sulfate, carbonate, silicate, hydroxide and phosphate salts).
In modern automatic dishwashing compositions a major inorganic builder ingredient, phosphate salts, are often replaced by citrate salts. The citrate salts are conveniently available in granular form, and can simply be dry-added to the compositions. However, cleaning adjuncts such as organic dispersants, which are very useful in nonphosphated compositions, are much more difficult to handle; their most common commercial form is that of a viscous aqueous solution. Of course the consequence of adding citrate and/or organic dispersants and removing phosphate or similar inorganic salts is that it becomes much more difficult to form discrete, crisp, free-flowing particles from the combined components in conventional agglomeration processes.
Moreover, it would be desirable to provide automatic dishwashing compositions incorporating an oxygen bleach system to replace chlorine bleaches. It is known, for example, that chlorine bleaches have certain disadvantages such as a tendency to darken silverware. Unfortunately, it can be very difficult to produce effective agglomerated nonphosphated automatic dishwashing compositions with appreciable contents of oxygen bleach systems on a commercial scale. Problems include that oxygen bleaches often take up more formulation space than chlorine bleaches, worsening the above-described processing problems since the bleach-active salts, such as sodium perborate, are too reactive to be used in wet mix/drying process stages. Also, there are problems of bleach stability and bleach compatibility with other ingredients in the compositions.
Accordingly, it is an object of the present invention to provide a new and improved process for making nonphosphated granular automatic dishwashing compositions comprising an oxygen bleach system (e.g., chelant plus perborate salts) and an organic dispersant. Another object herein is to provide such dishwashing compositions in the form of stable, free-flowing granules. These and other objects are secured, as can be seen from the following disclosure.